Gerry McCann asked a friend to check on his wife while she was left alone with their children the night their daughter went missing, it has been claimed.

According to sources, Gerry spoke to fellow doctor David Payne shortly before 6.30pm as he was having a tennis lesson and wanted him to check on Kate and the children.

Portuguese police believe the exchange shows that Gerry McCann was worried about his wife's state of mind just hours before four-year-old Madeleine was reported as missing.

The latest allegation comes as a Channel 4 documentary claimed the police in Portugal missed opportunities to find forensic evidence in the hours after Madeleine disappeared.

Professor Dave Barclay, a forensic analyst, told Dispatches the evidence might have cleared her parents of involvement on day one.

He said police should have been "more aggressive" in protecting the family's holiday apartment from being contaminated on May 3.

He told the programme: "It's clear that the forensic examination on the first day wasn't what we would have expected.

"There were opportunities missed. And one of those opportunities did a great disservice to the McCanns.

"Had they been more aggressive in protecting the apartment and doing a full forensic examination in that apartment it may have been that the McCanns were put completely out of it on day one."

The latest revelation that David Payne was asked to "stick his head round the door" to check on Kate and the children will be used by Portuguese police to back up their belief that Kate's mental state at the time was fragile.

Mr Payne was the last person outside the McCann family to see Madeleine alive before she vanished from their holiday apartment in Praia da Luz.

However, another friend said last night that Gerry had no concerns about whether or not Kate was coping with the children, but had just casually asked Mr Payne to look in on them.

Meanwhile, Prime Minister Gordon Brown has spoken to his Portuguese counterpart about the case.

The premier's spokesman said Mr Brown had raised the case with Portuguese Prime Minister Jose Socrates.

The spokesman said the two leaders, meeting in Lisbon for an EU summit, had a "brief discussion" about Madeleine.

Mr Brown's spokesman added: "They both agreed what matters was there should be the closest possible cooperation between the Portuguese and British police."